“It is not a concern” should alleviate any concern. 
But I appreciate remaining curious.
I suggest emailing jamesh@psaudio.com with your specific question and include the temperature reached by your unit. Ask if what you are specifically experiencing is too hot. He is good at tracking down information.
Being curious can be a curse, Elk Sometimes I think I came out of the womb asking “Why?”. I had only communicated with Paul and TJ. Thanks for tip. Maybe James can satisfy a loyal customer’s curiosity.
Ellk above suggested emailing jamesh@psaudio.com for an answer.
I don’t know how long you’ve had your unit. If it is not shutting down that is good. The remaining question is what is the longevity of parts at that sustained temperature.
It is a very legitimate concern, born of wanting to keep a piece of equipment we love as long as possible.
Perhaps James can shed light on it for you and you can share the answer.
My pleasure. Us young guys who have around for a while have to stick together.
Your BHK amps are likely only good for a year or so. I’ll take them off your hands for free when they reach that age.
I’m 99% sure that Paul said that temperatures of around 50 Celcius are normal because I was surprised how hot my pair of BHK250s get (they just drive the mids and tweeters). I’ll try to go back through my posts to find where Paul said this, and update this post when/if I track it down.
UPDATE - I’ve not managed to track down where Paul said that 50 Celcius is normal. I did however find some emails, dating back to mid 2018, between myself and PSA support because I had a problem where after a few hours the sound of my system would change dramatically. I thought, wrongly, that it was the amps running too hot - it wasn’t that, it turned out to be one of my P10s suddenly producing the wrong output voltage (well into the 250s when they should both be around 240v). PSA were very supportive in getting this resolved.
You might live to regret that offer
Seriously, in the automotive world there are surveys buyers can use to help their decisions: repair records, change of ownership, consumer satisfaction and other things.
Cars are worth compiling these stats on because they are expensive, but so is audiophile grade gear. Wouldn’t it be nice to not just read reviews, but know how audio gear buyers like their products, how often they needed repair, expected life expectancy, etc.? Something a little more scientific than forum comments.
I’ve never owned McIntosh audio gear but their reputation, based on shared owner experience, is that they are built to last. If I were told by a McIntosh staffer in the know that something is not a concern, the odds are that I would believe him or her without much elaboration.
PS Audio has a reputation for more affordable, musical gear. Saying that a product’s durability is not a concern, without elaboration, does not carry the same credibility. PS Audio does not emphasize longevity. Nor do we hear from satisfied very long-term owners. They may well be a silent majority. I hope that is the case.
Most audio companies don’t share durability information either. There is no durability competition in high end audio. McIntosh is in a league by itself with regards to durability. My point is that we have no reliable information about the likely lifespan of a PS Audio product.
The average lifespan of a BHK amp might be one year or many more. We just don’t know. We trust and hope that it will be more. And since I love PS Audio products, I hope that the company follows the trajectory of McIntosh and proves durable over time. We are making history!
That would be great, thanks!
I think you finally got to your actual point.
Indeed. I am endlessly curious and fully appreciate your wanting to know - even if it is just to know. 
I am here if you have questions. The BHKs should all run close to the same temperature but remember it also depends on the ambient room temperature as well as their environment. In MR2, the 300s are quite warm to the touch. My test is always to make sure I am comfortable placing my hand on them even after a good workout with loud music.
Their longevity will not be impacted by the heat they produce. These amps will go for decades.
This is what Nelson Pass has to say about the matter in his amplifiers: “The amplifier does not require any maintenance. While the design is conservative, this is a hard running amplifier, as single ended class A operation is the least efficient operating mode. In fifteen years the electrolytic power supply capacitors will get old. Depending on usage, you will begin to have semiconductor and other failures between 10 and 50 years after the date of manufacture. Later, the sun will cool to a white dwarf, and after that the universe with experience heat death.”
Seeing that PS Audio BHK’s are biased differently from Nelson’s class A amps, I would expect heat to be even less of an issue. Parts failure aside, worrying about the BHK longevity due to heat issues seems unwarranted.
I love that quote, Photon46. It’s good to know what Nelson Pass says on the subject. Even if something seems unwarranted, it does not hurt to understand why it is so.
What I am after is this: How would a customer know with some certainly that their own BHK amplifier is not running too hot to impact durability?
One way is by giving a range of acceptable fin temperatures. That is not published and many owners don’t have the right temperature gauge anyways.
The other way is the finger/hand test. It’s weak because different people have different tolerances for heat. However, something simple like “If you have to remove your fingers/hand from the fins after touching them for a couple of seconds, it’s running too hot” would suffice.
For me, it’s about being informed more than worrying about the longevity of my own BHK. I have small PC fans that run whisper-quiet on either side of the amp. They quickly dissipate heat from the sinks and make them cool to the touch.
Thanks, Paul. If I were to paraphrase what you are saying it would be: “If I hesitate to put my hand on the heat sinks for a couple of seconds for fear of burning it, the amp is likely running too hot.”
Absent a temperature range, that is guidance any concerned or simply curious owner can work with.
With regards to endurance, time will tell. Engineering can set expectations but BHKs are still children. When they get to be our age we’ll know for sure
Meantime, I’ll enjoy my 250, running with cool sinks from 2 small, whisper-quiet PC fans, one on either side. I suspect that it will likely outlive me.
Thanks, Elk, for understanding the need to understand
I am not sure what you see as the actual point, Ron, but yes, it does sometimes take conversation and approaching something from different sides to get clarity.
Hah! Well, hopefully you live long and prosper my friend.
Thank you, Paul. So long as I can be propped up in my recliner and continue listening to music I’ll be glad to reach 100 and beyond. Do I sound like Tom Brady?
That would give my BHK 250 a very long lifespan. I look forward to writing (perhaps dictating) a 30 year Pearl anniversary review.
But please, get those speakers done. I may not be able to have an all-PS Audio rig because of the turntable but I can change the label on my new generation Technics and make believe.
Different Class A bias setting maybe? One of my BHKs (ironically the one that never gave me one issue) always ran about 10-12 degrees hotter than the other…and both had equal ventilation.